Animal Behavior

Behavioral Ecology

Why is brown fat important to some animals that hibernate?

Many mammals have both brown and white adipose tissues (cells that store a large droplet of fat that swells when fat is stored and shrinks when fat is used for energy). They are both called triglyceride lipids, but brown fat tissue has the ability to generate heat. Although called brown, brown adipose tissue varies in color from dark red to tan, reflecting its lipid content. It is most commonly found in newborn animals and in most species, disappears by adulthood. But it does have some use, especially to mammalian hibernators: These animals have exceptionally well-developed brown fat (in fact, some scientists even refer to it as “the hibernation gland”). The supply of brown fat built up during the spring and summer and is then used during the winter months when the animal hibernates; thus, brown fat becomes an important tissue in the rewarming process that the animal undergoes after hibernation.